Devices for adjusting the position of cutting inserts in boring bars and other tools are known in the prior art. However, before such adjusting devices are described, a brief description of the mechanical context of such devices will be given.
Boring bars have a generally cylindrical bar body. A plurality of cutting inserts are mounted around the periphery of the body of the boring bar in recesses known as "pockets" that conform to the shape of two of the sides of the inserts. Each insert is secured into its respective pocket by means of a clamping screw which extends through a centrally-located hole in the insert. While pockets and clamping screws provide a secure mount for the inserts during a cutting operation, they do not, unfortunately, provide a system operator with any means for making fine adjustments in the position of the cutting edges of the inserts mounted around the periphery of the boring bar. This is unfortunate, since even small misalignments between the edges of the cutting inserts on the order of 0.001 inch can result in uneven wear of the inserts and a decrease in the performance of the boring bar. Even if the pockets were perfectly machined to the desired dimension, the inserts themselves can easily vary in size 0.001 of an inch or more due to manufacturing tolerances or uneven wear during use.
To solve this problem, devices for making small adjustments in the position of the cutting inserts in such tools were developed in the prior art. In one of the most common designs, one of the walls of the insert-receiving pockets in the tool body is replaced with a rectangular-shaped member known as a "cartridge" that is slideably mounted onto the body of the boring bar or other tool by means of a bolt. The cartridge is adjusted by one or more adjustment screws that are turned in order to slide the cartridge in a direction which can move the cutting edge of the insert either axially or radially with respect to the cutting edges of the other inserts mounted around the body of the boring bar.
While such prior art devices are capable of aligning the cutting edges of the inserts, the applicants have observed a number of shortcomings associated with such devices. For example, the metal-to-metal contact between the cartridges and the body of the boring bar often creates, on a microscopic level, an irregular sticking friction which results in irregular movement of the sliding wedge element as the adjustment screw is turned. Such friction coupled with the fact that even a partial turn of the adjusting screw moves the cartridge a relatively large distance on a microscopic level often causes the system operator to overshoot his intended positioning goal (which may be as small as 0.0005 inches). Overshooting of the positioning goal, in turn, requires the system operator to start over, thus creating an undesirable amount of unproductive downtime for the boring bar or other tool. Another shortcoming of such a design is that it requires the manufacture and assembly of additional precision parts onto the body of the boring bar. This of course results in higher manufacturing costs. Finally, it is possible for the adjustment screws used in such devices to loosen slightly from the vibrations associated with the machining operation, thus causing the cutting edge of the insert to shift out of position.
Clearly, there is a need for a mechanism for making fine adjustments to the position of cutting inserts mounted around a boring bar or other tool in order to eliminate undesirable marks in the workpiece which is easier and faster to use than prior art adjusting devices. Ideally, such an adjusting mechanism would require the manufacture and assembly of fewer precision parts so as to minimize the cost of the resulting adjustable boring bar or other tool, and would resist becoming loosened from the shock and vibration caused by the machining operation. Finally, it would be desirable if such an adjusting mechanism could be easily installed onto existing boring bars and other types of cutting tools.